1. Technical Field
The present invention relates to a liquid container containing a liquid which is to be supplied to a liquid ejecting apparatus.
2. Related Art
In the related art, as a type of a liquid container containing a liquid which is to be supplied to a liquid ejecting apparatus, there are an open type, an air tight type, and a semi-air tight type.
In the open type liquid container, air is introduced into a space (hereinafter, referred to as a “liquid containing space”), where liquid is contained, according to consumption of the liquid. For this reason, in the open type liquid container, a valve is provided to a liquid introducing hole so that the liquid in the liquid containing space is not leaked from the air introducing hole to an external portion of the liquid container. In addition, there is also a type where an air chamber is separately provided between the air introducing hole communicating with an external portion of the liquid container and the liquid containing space, so that the leakage of the liquid is prevented. In addition, in the liquid container, when a liquid ejecting apparatus does not consume the liquid, the liquid in the liquid container is maintained in a negative pressure state so that the liquid is not leaked from the liquid container to the liquid ejecting apparatus side. For this reason, in the case of using the open type liquid container, a negative pressure generating unit for maintaining the liquid in the negative pressure state is installed at the outlet side of the liquid container or the liquid ejecting apparatus side. Therefore, in the aspect using the open type liquid container, there is a problem in that it is difficult to miniaturize the apparatus due to the air chamber, the negative pressure generating unit, or the like.
On the other hand, in the air tight type liquid container, at least a portion of the liquid containing space is constructed with a flexible member, for example, a sheet. In the air tight type liquid container, no air is introduced into the liquid containing space, and the sheet is deformed according to the consumption of the liquid, so that the liquid containing space is reduced. In addition, the inner portion of the liquid containing space is maintained in the negative pressure state by a spring which pushes up the flexible sheet against the contraction of the flexible sheet. As a result, when the liquid ejecting apparatus does not consume the liquid, the liquid is not leaked from the liquid container to the liquid ejecting apparatus side. Unlike the open type liquid container, in the air tight type liquid container, since the air chamber or the negative pressure generating unit are not necessary, it is easy to miniaturize the apparatus. However, since the generation of negative pressure is dependent on the flexible sheet and the spring, the negative pressure is increased according to the consumption of the liquid. Accordingly, there is a problem in that a constant negative pressure is not implemented in a time interval from the time of starting the use of the liquid container to the time of ending the use thereof. In addition, as a result, there is also a problem in that the liquid which is not completely used remains in the liquid container.
As a type having both features of the open type liquid container and the air tight type liquid container, there is a semi-air tight type liquid container (for example, JP-A-2003-251826). Even in the semi-air tight type liquid container, at least a portion of the liquid containing space is constructed with a flexible member, for example, a sheet. According to the consumption of the liquid, the sheet is deformed, so that the liquid containing space is reduced. The semi-air tight type liquid container is also similar to the air tight type liquid container in that the negative pressure is generated in the liquid containing space by a spring biasing the flexible sheet.
However, in the semi-air tight type liquid container, an air introducing hole for introducing air into the liquid containing space is installed. In addition, at the time when the liquid containing space is somewhat reduced by the deformation of the sheet, the valve of the air introducing hole is opened, so that the air is introduced into the liquid containing space. As a result, the liquid containing space is slightly increased by the amount of the introduced air. At the same time, the negative pressure of the liquid containing space is slightly decreased (to be close to the atmospheric pressure). After that, in the semi-air tight type liquid container, the negative pressure is increased by the spring which pushes up the flexible sheet according to the consumption of the liquid, and every time when the air introducing hole is opened, the negative pressure is slightly decreased (to be close to the atmospheric pressure). This movement is repeated. As a result, except for the time just after starting the use of the liquid container, a negative pressure which is stabilized within a predetermined range in the time interval reaching the time of ending the use of the liquid container may be implemented. As a result, in comparison with the air tight type, the amount of the liquid which is not completely used but remains in the liquid container is also decreased.
However, in the aforementioned related art, a valve structure 590 of an opening portion 592 (air introducing hole) presses the opening portion 592 in the direction from an outer side of an container exterior 563 (liquid container) toward an inner side, so that the opening portion 592 is sealed. For this reason, in the case where the internal pressure of the container exterior 563 (liquid container) is increased due to the increase of the temperature of external air or the like, there is a problem in that the valve structure 590 is pushed toward the outer side of the liquid container and thus, the opening portion 592 is opened, so that the liquid of the inner portion is leaked.